Amiens has a northern French climate: not as wet as people fear, but rarely brilliant either. Summer (June–August) is the most pleasant, with warm enough temperatures for outdoor terraces and the hortillonnages boats running daily. The "La Cathédrale en Couleurs" light show runs in summer and is worth planning around.
Christmas brings a large seasonal market that fills the place in front of the cathedral — one of the best in northern France, running through December. Winter otherwise is grey and cold. The hortillonnages boat trips only run from April to October. Spring and early autumn are generally the best balance of weather and crowd levels.